Dial train friction device



Filed Jan. 273, 1968 INVENTOR. PAUL WUTHR/CH f A 7' 7' ORNE XS United States Patent M 3,487,633 DIAL TRAIN FRICTION DEVICE Paul Wuthrich, Woodbury, Conn., assignor to The United States Time Corporation, Waterbury, Conn., a corporation of Connecticut Filed Jan. 23, 1968, Ser. No. 699,846 Int. Cl. G04b 27/02 [1.8. C]. 58-63 6 Claims ABSTRACT OF THE DISCLOSURE A horological device, such as a watch, includes a mechanism to set the time indicating hands. The dial train, i.e., the group of gears which transmits power to the hands, is disconnected from the oscillator or its associated mechanism during the hand-setting operation. Such selective disconnection is obtained by a friction device which permits slippage during handsetting. The friction device includes a third wheel staff, a third wheel arbor positioned partly about a portion of the staff and having a slot, and a harp spring having one arm positioned in the slot of the arbor.

The present invention relates to horology and more particularly to a mechanism to obtain a friction-slip arrangement in a dial train.

A horological device, such as a watch or a clock, usually includes a power source, a timekeeping device, a dial train of gears and time indicating means, such as rotating hands. The power source is usually a mainspring or an electric battery. The timekeeping device is usually a balance wheeel or other type of oscillatory mechanism. The dial train consists of a series of gears, some of which are small and are called pinions, and others of which are comparatively large and are called wheels.

The time indicating hands are set, i.e., turned to their correct position, by means of a crown which is on the outside of the case. Usually the crown is pulled away from the case and rotated to set the hands. The hands must be set, for example, when starting the movement, when changing time zones or when correcting the time. The crown, in a mainspring driven watch or clock, may also be used to wind up the mainspring.

The crown is attached to a staff which carries a gear. That gear, either directly or by means of intermediate gears, turns the gears of the dial train. It is necessary that some of the gears of the dial train rotate in order that the hands may be set. The dial train gears serve two functions, at different times, namely, to turn the time indicating hands during the normal running of the movement and to set the time indicating hands.

The rotation of the crown and the setting of the hands should not damage the oscillator or escpaement. During such rotation, if the dial train is kept connected to the index wheel in an electric watch, or to the escape wheel in a mechanical watch, the pins on the lever or other of the delicate mechanisms may be injured. The dial train is usually disconnected from the index or escape wheel during the setting of the hands by means of a frictionslip mechanism. During normal operation of the movement, the friction connection is sufiicient so that power is transferred to the time indicating hands. However, the escapement or index wheel, either directly or indirectly, is kept from turning during the setting of the hands by a click, magnet or some other device. The index or escape wheel is held with sufficient strength during handsetting so that the friction connection is overcome, i.e., the connection slips, and the dial train is effectively disconnected from the index or escape wheel.

3,487,633 Patented Jan. 6, 1970 Various mechanisms have been proposed to obtain the friction connection in the dial train. For example, a coil spring may be compressed between the bottom surface of a pinion and a gear wheel. The spring is wound around the same staff upon which the pinion and the wheel are mounted. The pinion is attached to the staff and the wheel is mounted so that it may rotate relative to the staff. The spring provides a friction-fit of the wheel against a flange of the staff so that the wheel normally turns with the staff. That frictional force is overcome when the wheel is held fixed, during the setting of the hands, the pinion and staff then being free to rotate. This type of mechanism takes a considerable amount of space and is relatively costly.

A mechanism utilized in watches, for the purpose of obtaining a friction-slip, consists of a number of protrusions on the inside wall of a tubular cannon pinion. The protrusions may be formed by indentations in the wall of the tubular portion of the cannon pinion. The protrusions rub against the seconds staff, which is within the tube of the cannon pinion. During normal running of the watch, the friction between the center arbor and the cannon pinion is sufficient so that the rotation of the center arbor carries the cannon pinion with it. During hand setting, the center arbor is held fixed and the cannon pinion rotates by overcoming the friction. This type of device is inexpensive. However, it is not accurate as it is difficult to consistently reproduce the exact desired friction due to tolerance variations in the diameter of the arbor and the cannon pinion and the size of the protrusions.

It is the objective of the present invention to provide a mechnaism to provide a friction-slip in a horological dial train, which mechanism is relatively inexpensive, may be readily assembled and repaired, and which provides an accurate and constant predetermined amount of friction.

In accordance with the present invention, a dial train friction-slip device is provided. This device is particularly adapted for use in an electric battery powered wrist watch. Preferably the friction mcehanism of the present invention provides a frictional connection between the friction pinion staff and an arbor attached to the third wheel. A spring is used which is about U-shaped, i.e., a harp spring. One arm of the spring bears against the friction pinion staff. The other arm of the spring acts against an arbor on the third wheel, normally urging the third wheel arbor and the friction pinion staff to rotate together.

Other objectives of the present invention will be apparent from the following detailed description of a preferred embodiment taken in conjunction with the accompanying drawings.

In the drawings:

FIG. 1 is a side cross-sectional view of a portion of a watch movement; and

FIG. 2 is a sectional view taken along lines AA of FIG. 1.

The description which follows is directed to a wrist watch which is powered by an electric battery. The battery supplies current to a coil mounted on a balance wheel. The coil interacts with one or more magnets fixed on the frame of the watch. The current is supplied intermittently, either by means of contacts or an electronic circuit. The movement of the balance, either directly or indirectly through a lever, is transmitted to an index wheel. The index wheel, usually by means of a pinion, is connected with a seconds wheel, i.e., a fourth wheel. The fourth wheel is fixed on a fourth wheel staff which carries the seconds hand on its end. A pinion is connected to, or is integral with, the fourth wheel staff. That pinion,

3 called the fourth pinion, meshes with the third wheel. The drawing of FIG. 1 shows the third wheel and its immediate mechanism.

In the embodiments described herein, the friction device is used in the environment of the third wheel of an electric battery powered watch. However, the friction device of the present invention may also be used on other Wheels of electric powered watches of various types or in connection with mechanical, electrical or otherwise powered watches, clocks and other horological instruments.

In the drawing of FIG. 1, the main (front) frame plate 1 of the watch movement has a cavity 2 at the bottom of which there is a hole 3. A train bridge 4 is kept separated from the frame plate 1 by pillars or other means (not shown).

One end of the fourth wheel (seconds) staff 5 rotates in hole 6 in the train bridge 4. A pinion 7a and a fourth Wheel (seconds wheel) 7b are fixed on the seconds staff 5. The fourth wheel staff 5 rotates within a tube 8 fixed within a hole in the frame plate 1. A second tube 9 rotates about tube 8. The center Wheel 10 is attached to the tube 9.

The center wheel 10 meshes with the friction pinion 11. One portion of the staff 12 of the friction pinion 11 rotates within the hole 3 of the frame plate 1. The staff 12 is integral with, or attached to, the pinion. The staff 12 consists of an enlarged portion 13 on one side of the frame plate, a smaller circular portion 14 which rotates within hole 3, an elongated circular portion 15 slightly smaller in diameter than its portion 14, a cylindrical tapered portion 16 the bottom of the taper being integral with its portion 15, and a top portion 17 having a beveled edge and a flat top 17a. The circular portion 15, tapered portion 16 and top portion 17 of staff 12 are substantially covered by a third wheel arbor 18. The third wheel arbor 18 has a bottom shoulder 19 which rests on the flange 20 of pinion staff 12. The center hole 21 or arbor 18 is rotatable, with a clearance, about the circular portion 15 of staff 12. A center portion 22 of arbor 18 fits over the tapered portion 16 of the staff. A top inverted bowl-like portion 23 of the arbor fits over the top portion 17 of the staff. A circular shaft 24 protrudes from portion 23 of the arbor 18 and rotates in hole 25 of the train bridge 4.

The arbor has a slot 31 in its center portion 22. The slot 31, as seen in FIG. 2, is about the form of a chord and is sufficiently deep so that the tapered portion -16 of staff 12 is exposed.

A harp spring 32, in the general form of a U, has a straight arm portion 26 which is positioned in the slot 31. The spring 32 also includes a U-shaped center portion 27, a straight arm portion 28, a short portion 29 angled inward to portion 28, and a short portion 30 angled outward to portion 29. The outer surface of center portion 22 of the arbor fits in the angle formed by portions 28 and 29 of the spring 32.

The spring 32 urges the hole 33 in the center portion 22 toward the tapered portion 16 of the staff. The pressure of the spring 32 against the tapered portion 16 urges the staff 12 into the third Wheel arbor 18. The staff 12 is thereby prevented from falling out (away from frame 1) by the spring 32. The third wheel 34 is fixed on the top portion 23 of the third wheel arbor. The third wheel 34 meshes with the fourth wheel pinion 7a.

In the process of assembling the watch the third wheel 34 is attached to the top portion 23 of the third wheel arbor 18. The harp spring 32 is positioned on the center portion 22 of the third wheel arbor 18. The third wheel 34, the third wheel arbor 18, and the harp spring 32 form a sub-assembly. This sub-assembly is preferably placed on the front frame 1, although it may alternatively be assembled to the train bridge 4. The train bridge 4 is then assembled in position (spaced away from the front frame 1), for example, by pillars and screws or other spacing means. The shaft 24 is positioned within the hole 25 of the train bridge 4 during assembly of the train bridge to the movement. At this point in the assembly process, after the frame and train bridge are assembled, the sub-assembly, consisting of the third wheel 34, the third wheel arbor 18 and the harp spring 32, is in its position between the front frame plate 1 and the train bridge 4. The arbor is held substantially upright and aligned in position because of the support of the cylindrical wall of cavity 2 on the cylindrical external wall of the lower portion of the third wheel arbor 18. The sub-assembly is positioned so that the center hole 21 of the third wheel arbor 18 is substantially aligned iWth the hole 3 of cavity 2 within frame plate 1.

The friction pinion 11 may now be assembled in the movement. This is accomplished by inserting the top portion 17 of the friction pinion staff 12 through hole 3 in frame plate 1 and hole 21 in the third wheel arbor 18. When the friction pinion 11 is inserted, the beveled edge of its top portion 17 spreads the harp spring 32 and permits the passage of the top portion 17.

As an alternative assembly procedure, first the friction pinion 11 may be inserted through its hole 3 in frame plate 1. The third wheel arbor sub-assembly may then be snapped in place over the friction pinion. The train bridge would then be assembled in place over the third wheel pinion.

The structure of the components of the mechanism of the present invention provides advantages in the assembly operation. The beveled edge on the top portion 17 of the friction pinion 11 forces the spring 32 openwithout the necessity of manually opening the spring. The cavity 2 of the frame plate 1 provides a means for temporarily holding the third wheel arbor substantially properly aligned. The taper of the tapered portion 16 of the friction pinion staff cooperates with the inward force of the harp spring 32 to provide a draw movement which holds the friction pinion staff within the third wheel arbor. The construction of the third wheel arbor and the friction pinion, in separate pieces, enables them to be assembled through a relatively small hole 3 having a relatively low bearing friction. If, alternatively to the structure of the present invention, the third wheel arbor and friction pinion were constructed in one unitary piece, the hole in the front frame plate 1 would have to be sufficiently large for the insertion of the friction pinion 11. Such a large hole would require a larger shaft and have increased bearing friction. The two-piece construction of the friction pinion and the third wheel arbor enables the friction pinion to be removed and replaced without removal of the third wheel arbor sub-assembly (the third wheel arbor, the third wheel and the harp spring).

Modifications may be made in the present invention.

What is claimed is:

1. In a horological movement having time indicating means, a plurality of frame members, a timekeeping oscillator, a dial train including a plurality of gears mounted on staffs and means to set the time indicating means, a friction-slip mechanism to disconnect at least part of the dial train from the oscillator, said friction-slip mechanism comprising a gear attached to a staff, said staff being rotatably mounted in a first frame member, an arbor fitting at least partly over said staff and having a slot, said arbor including a staff portion protruding from its top and rotatably mounted in a second frame member, and a spring positioned at least partly in said slot and urging the arbor and staff to rotate together, wherein said staff includes a tapered portion against which the spring bears to retain the staff within the arbor.

2. A horological movement as in claim 1 wherein the movement is a watch and the gear is a pinion meshing with the center wheel,

3. A horological movement as in claim 1 wherein said staff has a shoulder portion against which the lower edge of the arbor rotatably bears.

5 6 4. A horological movement as in claim 1 wherein the References Cited movement is a watch and the arbor is attached to the FOREIGN PATENTS third wheel which meshes with the fourth Wheel pinion.

5. A horological movement as in claim 1 wherein the 241707 8/1946 swltzerland' Spring is a harp'shaped SPring- 5 ROBERT S. WARD, JR., Primary Examiner 6. A horological movement as m claim 1 wherein the GEORGE H. MILLER, JR. Assistant Examiner movement is a Watch having a frame plate and a train bridge, the frame plate being the first frame member and U L the train bridge is the second frame member. 58138 

